This invention relates generally to patching roofing assemblies for the roofing and construction industry. More particularly, this invention relates to the patching of single ply roof membranes especially covered with sheets of flexible material such as chlorosulfonated polyethylene.
In certain modern roofing installations for commercial buildings, a layer of insulation is secured to the deck of the roof and this is covered with sheets of flexible material such as chlorosulfonated polyethylene. Adjacent margins of adjacent sheets are sealed together in overlapping relationship and thus the sheets form a sealing membrane over the insulation.
The sheets which form the membrane are secured to the insulation and the underlying roof deck at spaced locations by fastener assemblies which are spaced along the margins of the sheets. Each fastener assembly comprises a washer-like disc made of plastic or metal and further comprises a screw adapted to thread into the roof deck to cause the disc to clamp the membrane downwardly against the insulation. Roofs of this type are known as single ply roofs.
After long evaluation of various membrane polymers such as EPDM, PC, CPE and chlorosulfonated polyethylene (available from DuPont under the trademark HYPALON) many engineers in the field have chosen chlorosulfonated polyethylene as the membrane of choice in single ply roofing. Chlorosulfonated polyethylene is unique in that it is a thermoset synthetic rubber which, in its initial installed form, is thermoplastic in nature which allows chlorosulfonated polyethylene derived one ply membrane to be hot-air welded. Hot-air welding is accepted in the industry as the most reliable form of single-ply membrane seaming. A hot-air welded seam can be made as strong as the membrane itself.
Chlorosulfonated polyethylene has a polyethylene backbone with occasional --Cl and SO.sub.2 Cl groups. A unique property of chlorosulfonated polyethylene is its ability to cure into a crosslinked rubber after installation and exposure to the natural elements. This is made possible by the aforementioned sulfonyl chloride groups contained along the polymer chain. When exposed to moisture and ultraviolet light on a roof, the groups form metal sulfonated cross links. The result is a progressive surface curing, or crosslinking, which actually adds strength and durability to the installed roof.
In one known installation technique, hot-air welds lifts the membrane edge, exposing inner surfaces to a controlled stream of superheated air. The thermoplastic rubber (HYPALON derived membrane) softens and is pressed together, fusing into a seam that can be made as strong as the membrane itself.
Outstanding weatherability and UV resistance has been demonstrated in various natural sunlight accelerated weathering tests. In real-time tests, including some actual roofing installations over thirteen years old, the chlorosulfonated polyethylene derived membrane continues to perform well, remaining watertight and highly reflective. UV resistance is critical to any roofing membrane, since the ultraviolet component of sunlight is by far the most destructive natural force on a roof. The chlorosulfonated polyethylene derived membrane is highly resistant to UV. Chlorosulfonated polyethylene derived membrane has been used for over 30 years in many severe weathering exposures with successful results.
Another great advantage of chlorosulfonated polyethylene derived single membrane roofing systems is that it weight only 33 pounds per square as compared to graveled built-up systems weighing up to 600 pounds or ballasted systems that weight up to 1500 pounds per square.
Ease of repair is a key requirement for any single ply roofing membrane. The addition of rooftop equipment, mechanical damage from natural forces or human error can necessitate a repair to even the best roofing system. Accordingly, single ply roofs at time will need repair, known as "patching". While well suited for its intended purposes, new methods for patching such single ply roof systems that are both easy and inexpensive as well as providing a patch that is as strong as the original membrane is required for chlorosulfonated polyethylene derived membrane roof systems.